I think the HF kit has a M8x1 fitting which is the one you need. That kit is also mentioned in the “1981 – 1985 300SD 722.3 and 722.4 Transmission Adjustment Guide” by Peter Keun that I found online.

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1985 300CD, CA
172 Anthrazitgrau/Palomino 154

1985 300TD, CA
040 Schwarz/Palomino 154/3rd row seat

1985 300TD, CA
473 Champagner/Palomino 154/Cargo cover